My work on compiling data for a "simple" 1970-1980 VIN decoder presses on. Some models are harder to pin down than others, especially when trying to reconcile the annual production figures in the Production Models book with the serial numbers I'm seeing harvested from eBay.

The main question I'm trying to work out is, how were serial numbers assigned? Did every series/engine designation start from zero? For example, was there a 109056xx000001 and a 109057xx000001 or did they share a common production line and number 000001 could have been a 109.056 and 000002 could have been a 109.057?

The best evidence I have of this is the early '70s 280SE coupe/cabriolet, which the only way the serial numbers seem to track the annual production is if they're added together. And if so, was that only for some chassis and not others?

The 600, 6.3, 220-280SE coupes and cabs were called "off line" cars, which were built by assembly teams rather than run down the production assembly line.

As you most likely know the first six numbers are the chassis/model, the next two are the engine and transmission type, and the last six are the actual sequence in the production.

I remember the serial number on my 1970, 250/8 was 114.010-12-042788.

One dynamic on the "off-line" cars, particularly the 600, is that the assembly teams did not always place components in exactly the same spot... When I was "in the business" long ago, I heard mechanics "cuss" about this on more than one occasion.